Abstract:

Nowadays, most of the isobutene was obtained as a by-product from both thermal and catalytic cracking processes. Due to growing of demand, butane dehydrogenation to produce isobutene is a valuable process in petrochemical industry. Traditionally, high purity isobutane is used as feedstock for producing isobutene, in which purification process is complex and cost high. In this paper the dehydrogenation process using mixed low hydrocarbons as raw material to produce isobutene was studied over Pt-Sn/Al₂O₃ catalyst, and the effect of Pt content, Pt/Sn atomic ratio and chlorine content on isobutane conversion and isobutene selectivity were investigated. The results show that the conversion increases with Pt content from 0.20% to 0.40%(mass）and decreases when it is larger than 0.40%（mass）.The maximum conversion, 35%(vol）even after 8 hours, and the maximum yield of isobutene are obtained at 0.40%(mass）because of smaller particle size and better dispersion of platinum, as shown by TEM results. For the effect of Sn addition, the conversion and the selectivity increase first and then decrease with the Pt/Sn atomic ratio. There is the maximum conversion for the catalyst with Pt/Sn atomic ratio 1∶1, the maximum yield 26% for that with Pt/Sn atomic ratio 2∶3 even after the reaction time of 8 hours. The chlorine content in catalyst was measured by potentiometric titration. The data show that the conversion increases with increase of the chlorine content, while the selectivity declines. There is the best catalyst performance for the catalyst with 0.87%(mass）chlorine.

摘要：

采用炼厂异丁烷塔顶轻组分作为原料，运用Pt-Sn/Al₂O₃为脱氢催化剂生产异丁烯。通过制备不同的铂锡催化剂考察影响催化剂性能的各种因素。结果表明，异丁烷的转化率随着Pt含量的增加先增大后减小，在0.40%左右达到最大值，反应8 h后仍然保持在35%以上，同时异丁烯的收率也能保持在22%以上。异丁烷的转化率和异丁烯的选择性均随Pt/Sn原子比的增大呈现先增大后减小的趋势，并且在Pt/Sn原子比为2∶3时，异丁烯的收率达到最大，反应8 h后仍能达到26%以上。通过碱溶电位滴定法分析催化剂中的氯含量，研究了氯含量与催化剂性能的关系。结果表明，随着氯含量增大，异丁烷的转化率不断上升，而异丁烯的选择性不断下降。综合考虑异丁烯的收率和转化率及选择性，催化剂中氯含量为